ideas about a unioning file system

[Mohammad Nayyer Zubair]

Hi.

We are currently designing a stackable, fan-out file system, similar in
principle to the freebsd unionfs filesystem, at the Files and Storage
Lab at Stony Brook University.

We intend to use the FiST (http://www1.cs.columbia.edu/~ezk/research/fist/) stackable templates.

Has anyone extensively used freebsd unionfs? From a system/network
administrator or from a kernel developer standpoint, what do you like
about it and what you dont like about it?

How should a unioning filesystem should behave? What specific features
would you like it to have?

Out of the previous efforts at a unioning file system like the Sun's TFS,
3DFS, Plan 9 and FreeBSD unionfs itself, which fs do you think came close
to an ideal unioning file system?

I would really appreciate if you can share any thoughts, ideas, comments
on designing such a file system.

Mohammad Nayyer Zubair